United States v. O'brien, 391 US 367 - Supreme Court 1968

"[A] government regulation is sufficiently justified if it is within the constitutional power of the Government; if it furthers an important or substantial governmental interest; if the governmental interest is unrelated to the suppression of free expression; and if the incidental restriction on alleged First Amendment freedoms is no greater than is essential to the furtherance of that …

And "when `speech'and `nonspeech'elements are combined in the same course of conduct, a sufficiently important governmental interest in regulating the nonspeech element can justify incidental limitations on First Amendment freedoms. "

It is a familiar principle of constitutional law that this Court will not strike down an otherwise constitutional statute on the basis of an alleged illicit legislative motive

We cannot accept the view that an apparently limitless variety of conduct can be labeled `speech'whenever the person engaging in the conduct intends thereby to express an idea

—a registrant under Selective Service who burned his draft card in protest of the war in Vietnam could be prosecuted.

—as of the limitless variety that cannot be labeled as speech for protection within the meaning of the First Amendment.

A content-neutral restriction, on the other hand, triggers intermediate scrutiny, which only requires the government to prove that the restriction serves a substantial governmental interest; that the interest served is unrelated to the suppression of free expression; and that the restriction does not burden substantially more speech than is necessary to further the government's …

"What motivates one legislator to make a speech about a statute is not necessarily what motivates scores of others to enact it, and the stakes are sufficient high for [the court] to eschew guesswork."